COMPARATIVE EVALUATION OF PURE AND COMMERCIAL ALUMS IN WATER TREATMENT

Abstract

chemical for the removal of colloidal substances and other finely suspended materials contributing to the turbidity of water. In the laboratory, for testing water and for the determination of optimum alum dose of water to be treated, pure alum is used; whereas, in the field, for the treatment of turbid surface water, commercial alum is used. In 4 types of water samples viz., high alkalinity and low turbidity; high alkalinity and high turbidity; low alkali-nity and low turbidity; low alkalinity and high turbidity, these two alums were applied to determine their optimum alum doeses. Column settling studies for the 4 types of water with both the alums were conducted to determine the settling vela. cities of flocs and surface overflow rates etc. As for a comparison, canal water was also analyzed with these two alums. From the findings and results of analysis e.g. deter-mination of water quality parameters, residual alums, column settling tests etc., it is clear that pure alum is better cosiTtaant for high turbid waters and commercial alum for low turbid water. This is due to the fact that commercial alum contains lots of impurities, which helps in flocculating the suspended and colloidal impurities in water. Pure alum contains no impurities, and hence suitable for highly turbid water) for easy flocculation. In case of removing the suspended solids, both alums can remove at maximum 98 and minimum 8X. The pH of the effluents of pure and commercial alums are always less than the pH of influent, showing that alum salts are acidic in nature. Both alums can not remove hardness significantly